Gas injection system for energetic-beam instruments

ABSTRACT

A gas injection system for an energetic-beam instrument having a vacuum chamber. The system has a cartridge containing a chemical serving as a source for an output gas to be delivered into the vacuum chamber. The cartridge has a reservoir containing the chemical, which rises to a fill line having a level defined by an amount of the chemical present in the reservoir at a given time. An outlet from the reservoir is coupled to an output passage through an outlet valve and configured so that when the system is tilted the outlet remains above the level of the fill line. Embodiments include isolation valves allowing the cartridge to be disconnected without destroying system vacuum.

CLAIM FOR PRIORITY

This application is a continuation of U.S. patent application Ser. No.13/864,362, filed Apr. 17, 2013; which application claims the priorityof U.S. Provisional Patent Application, Ser. No. 61/671,473, filed Jul.13, 2012; both of which applications are incorporated in theirentireties by reference into the present application.

BACKGROUND

1. Technical Field

This disclosure relates to the removal of specimens insideenergetic-beam instruments, such as focused ion beam (FIB) microscopesand the preparation of specimens for later analysis in the transmissionelectron microscope (TEM) and elsewhere, and apparatus to facilitatethese activities.

2. Background

The use of in situ lift-out (INLO) for TEM sample preparation in thedual-beam FIB has become a popular and accepted technique. The INLOtechnique is a series of FIB milling and sample-translation steps usedto produce a site-specific specimen for later observation in a TEM orother analytical instrument. Removal of the lift-out sample is typicallyperformed using an internal nanomanipulator in conjunction with theion-beam assisted chemical-vapor deposition (CVD) process available withthe FIB tool. A suitable nanomanipulator system is the OmniprobeAutoProbe 300, manufactured by Omniprobe, Inc., of Dallas, Tex. Detailson INLO methods may be found in the specifications of U.S. Pat. Nos.6,420,722 and 6,570,170. These patent specifications are incorporatedinto this application by reference, but are not admitted to be prior artwith respect to the present application by their mention in thebackground.

Gas chemistries play an important role in INLO. Gas injection in the FIBmay be used for etching to speed the milling process, for ion orelectron-beam assisted CVD of oxides, metals and other materials, fordeposition of protective layers, and for deposition of planarizingmaterial, such as silicon dioxide, to fill holes where lift-out sampleshave been excised. For a number of reasons, gas injection systemsmounted on the wall of the FIB vacuum chamber have become preferred.This offers a safety advantage over injection systems using gas sourcesor bottled gases that are external to the FIB vacuum chamber.Chamber-mounted injection systems also permit whole-wafer analysis andcan be easily inserted to place a gas nozzle near (within 50 μm) theposition where the charged particle beam strikes the sample. Aftercompletion of the injection process, the system can be retracted to asafe position for normal FIB sample translation operations. An exampleof a gas injection system is disclosed in US Patent Publication No.2009/0223451. This patent specification is incorporated into thisapplication by reference, but is not admitted to be prior art withrespect to the present application by its mention in the background.

There are a growing number of gas chemistries of interest andresearchers typically require more than one chemistry on the sameinstrument. This is commonly achieved by installing additional gasinjection systems that use up additional ports on the instrument. Eachgas injection system has to be customized to suit the instrument andport and reagent being used. For example, there may be an“inappropriate” port on a certain instrument that, although unoccupiedand thus available for mounting a gas injection system, would orient agas injection system at an angle that would adversely affect the gasinjection system's performance (e.g. allowing flow of a liquid sourceinto the delivery path, resulting in release of a liquid undesirablyinto the instrument vacuum chamber). Thus there are a limited number ofappropriate ports on a typical FIB, and a growing number of desiredaccessories that may need to be installed on these ports. Therefore,providing additional gas chemistries will not only be costly, but canalso compromise the flexibility for a researcher to use other accessoryinstrumentation. A solution is required that can be easily adapted foruse on a variety of energetic beam instruments and which offers theresearcher a safe and efficient way to use more than one gas chemistrywithout compromising the other uses of the microscope.

DRAWINGS

FIG. 1 is a schematic diagram of the connection of cartridges to a gasinjection system.

FIG. 2 is a schematic diagram of another embodiment of a gas injectionsystem.

FIGS. 3 through 5 show details of a cartridge holding liquid or finepowder at different orientations.

FIGS. 6 through 8 show details of a cartridge holding pellets of achemical at different orientations.

FIGS. 9 through 11 show another embodiment of the cartridge at differentorientations.

FIG. 12 is a schematic diagram of a complete gas injection system,according to the present disclosure.

FIG. 13 is a schematic structural diagram of the gas injection systemmounted to the vacuum chamber wall of an energetic-beam instrument.

FIGS. 14 and 15 are flow charts showing methods of operating the gasinjection system.

DETAILED DESCRIPTION

This disclosure relates to a multiple gas source chamber-mountedinjection system that only requires use of a single port and can beinstalled on a variety of different instruments and ports with a varietyof angles. To save interrupting experiments, sources can be exchangedeven while the instrument is evacuated and safety is assured byautomatic recognition of the source type. Not only does the usageefficiency of existing ports improve, but with a multiple gas sourcechamber-mounted injection system, a complex and automated process flow,or schedule, involving different gas sources over a timed depositionperiod is possible. The individual sources can be maintained atdifferent temperatures to maintain the desired vapor pressure in eachtube, and feedback from sensors can be used to adjust the depositionparameters and maintain them within the correct limits.

Removable cartridges for gas sources that can be exchanged quickly andeasily offer several advantages. They allow a multitude of sources to beoffered on a single gas injection system, require only a single port onthe vacuum chamber for the delivery of multiple gases, and broaden therange of sources quickly available beyond the number that may byphysically mounted and residing on the gas injection system at any onetime. This adds additional flexibility and the capability to meet amultitude of gas injection needs without consuming additional spaceeither on the gas injection system (for more resident gas sources) or onthe vacuum chamber (for more gas injection systems), and reduces theneed to purchase additional energetic-beam microscope instruments.Further, research capacity is expanded without requiring the purchase ofa second gas injection system, offering additional economic advantages.The inclusion of an auto-identification capability for gas sourcecartridges facilitates plug and play functionality. Auto identificationcan reduce or eliminate the requirement for operator interaction tomanually adjust the controller to accommodate a source change, andenhances safety by eliminating the opportunity of operator error whenmanually adjusting the controller. If cartridges are mounted indifferent positions on the gas injection system, the auto-identificationfeature, when used with proper control software, can help ensure thatthe correct gas flows when called for in a stored recipe, regardless ofthe actual position of its cartridge on the system.

To fully enable a removable cartridge solution, it is advantageous tochange sources rapidly. Enabling the exchange of removable cartridgeswhile the energetic beam microscope is under vacuum helps to achievethis goal. Gas injection systems that mount directly to an energeticbeam microscope commonly require venting the microscope to gain accessto the gas sources. This is because existing conventionalchamber-mounted systems are deliberately designed so that gas sourcesare always connected to the vacuum in the chamber while the gasinjection system is mounted. In some existing systems, the gas chemistryreservoir itself resides inside the vacuum chamber. In this case,adding, removing, or exchanging gas reservoirs requires opening thechamber, which not only can cause significant downtime (anywhere from 10minutes to 24 hours depending on the size of the chamber and baselinevacuum level desired), but can also result in undesirable contaminationof the chamber from opening the chamber to atmosphere. Contaminationleads to even more downtime as the chamber is cleaned, or alternately,may deleteriously affect the quality of the experiment if the chamber isnot cleaned. Herein the term vent-free refers to the capability ofchanging cartridges without venting the vacuum chamber (opening it tothe atmosphere). Vent-free embodiments, as provided herein, enable plugand play functionality while eliminating the negative repercussions fromventing the energetic-beam microscope.

Referring now to FIG. 1, a gas injection system (1000) is providedcomprising cartridges (100) capable of holding chemicals (180) orchemical precursors that serve as sources for gases that will bedelivered into the vacuum chamber (240) of an energetic-beam instrument,such as a focused ion beam microscope (FIB) or scanning electronmicroscope (SEM). FIG. 1 shows the general layout of the cartridges(100) of an embodiment. One or more cartridges (100) are connectedthrough isolation valves (220) to a delivery path (230). The deliverypath (230) is shown here as including a manifold (250) converging to asingle delivery line (234) that enters the vacuum chamber (240) of theinstrument at a port (245) in the vacuum chamber (240), and terminatesinside the vacuum chamber in a nozzle (320) for delivering the outputgas to a sample in the vacuum chamber. This configuration allows theoutput gases from one or more cartridges to be mixed as desired and/ordelivered by nozzle (320) to the same area of a sample. Each cartridge(100) has internal valving (discussed below) and a reservoir (110) forholding a chemical (180) or chemical precursor capable of serving as asource of an output gas, each called a “chemical” here. Each cartridge(100) also has an identification device (200) connected to a recognitiondevice (210), so that characteristics of a given cartridge (100) such asthe identity of its contents may be identified to a controller (270),here drawn as a programmable computer, for control of processes(discussed below). FIG. 2 is a schematic diagram of an alternativeembodiment having one isolation valve (220) in the delivery path (230)instead of one per cartridge (100).

FIGS. 3 through 5 show details of a cartridge (100) holding chemical(180) in the form of a liquid or fine powder at different orientations.The reservoir (110) of each cartridge (100) has an inlet (120) coupledto an input valve (130). The input valve (130) is coupled to an inputpassage (140) for the selective input of carrier gases. The input valve(130) can be a controllable input metering valve, or can include anadditional input metering valve. The reservoir is preferably connectedto a heater (115) for heating the chemical (180) contents. Additionalheaters may be distributed throughout the gas injection system (1000)for controlling the distribution of temperatures along the delivery path(230).

The reservoir (110) has an outlet (150) for the output of the chemical(180), possible mixed with a carrier gas. The outlet (150) is connectedto an output valve (160) and from that point to an output passage (170).This output valve (160) can be a controllable output metering valve, orcan include an additional output metering valve. As shown in FIG. 1, theoutput passage is further connected to an isolation valve (220) for thepurpose of selectively isolating the cartridge (100) from the atmospherewithin the vacuum chamber (240) of the instrument.

The reservoir (110) may have a separate port (not shown) for fillingwith chemical (180) prior to use in the gas injection system (1000), orthe reservoir may be filled through the input passage (140) or theoutput passage (170).

The chemical (180) in the reservoir (110) rises to a fill line (190),usually predetermined by the amount of chemical (180) previously placedinto the reservoir (110). The inlet (120) and outlet (150) of thecartridge (100) are disposed so that at the various tilt angles shown inthe drawings (FIGS. 3 through 5), the outlet (150) remains above thefill line (190), so that a chemical (180) in liquid or fine powder formis prevented from directly entering the vacuum chamber (240) while thedesired output gas is delivered to the vacuum chamber (240). In general,the reservoir (110) is capable of being heated to cause the chemical(180) to vaporize and, possibly joining with a carrier gas from theinlet (120), to flow into the outlet (150). In this way, the bulkchemical (180) does not enter the outlet (150) and the vacuum chamber(240), only the output gas, which is possibly combined with a carriergas that enters the gas injection system through an input passage (140)of a cartridge (100) or perhaps through an auxiliary carrier gas inputpath (350) as shown in FIG. 12. It is generally preferable, but notessential, that inlet (120) be disposed to remain below fill line (190)at various tilt angles in order to allow an input gas to flow throughthe chemical (180).

The reservoir (110), or the chemical (180) within the reservoir, canserve as a source for an output gas in any one of a variety of ways, aswill be appreciated by those skilled in the art. For example, FIGS. 6through 8 show a similar arrangement of the cartridge (100), where thechemical (180) comprises relatively large pellets. Such large pelletscan be composed of a material that has a nanoporous large surface areathat can adsorb and retain a useful amount of output gas at roomtemperature, and that when heated can desorb the output gas at a usefulvapor pressure for delivery. This technology has been developed for safestorage and delivery of toxic gases into semiconductor processingequipment. A commercially available deposition precursor source in theform of nanoporous pellets is exemplified by the SAGE™ (Sub-AtmosphericGas Enhanced) technology developed by ATMI, Danbury, Conn. These pelletsalso define a fill line (190), which remains below the outlet (150) asthe cartridge (100) is tilted.

FIGS. 9 through 11 show an alternative embodiment, where the inlet (120)and outlet (150) further comprise an inlet dip tube (125) and an outletdip tube (155). It will be apparent to those skilled in the art that diptubes or other devices or structures having an inlet (120) or outlet(150) may be used, so long as the inlet (120) and especially the outlet(150) remain disposed as described above. It will also be apparent thatthe same type of device or structure need not be used for both inlet(120) and outlet (150).

FIG. 14 shows a flow chart of a method for supplying a gas according tocartridge (100) characteristics. In step 302, the user provides acartridge (100) enclosing a source of gas; in step 304 the cartridge(100) is removably connected to the vacuum chamber (240) at a port (245)as described above, through the mechanisms of the gas injection system(1000). In step 306, one or more characteristics of the cartridge (100)are automatically identified, and in step 308 the gas injection system(1000) controls a flow of gas according to the cartridge (100)characteristics. FIG. 15 shows further detailed steps in the method,including some optional steps. At step 310 the gas injection system(1000) transmits cartridge (100) characteristics to a controller (270).At step 312 the controller (270) is optionally connected to a pressuresensor (280). At step 314, the flow of gas may be controlled in responseto a sensor signal. At step 316 there may be optional evacuation of thedelivery path through an evacuation path (300).

FIGS. 12 and 13 show an embodiment of the gas injection system (1000)for an energetic-beam instrument having a vacuum chamber (240), wherethe gas injection system (1000) comprises a chassis (360) mounted to thevacuum chamber (240) at a port (245); a removable cartridge (100)supported upon the chassis (360) and having an interior and an exterior,and capable of containing a chemical (180) serving as a source for anoutput gas, the removable cartridge (100) comprising an output passage(170) through which the output gas may flow from the interior to theexterior of the cartridge (100); a delivery path (234) having aconductance and connecting the output passage (170) of the removablecartridge (100) to the vacuum chamber (240), through which the outputgas is delivered into the vacuum chamber (240); and, an isolation valve(220) in the delivery path (234), whereby the cartridge (100) may beremoved while the vacuum chamber (240) remains under vacuum when theisolation valve (220) is closed.

FIG. 13 also shows the delivery path (230) terminating in a nozzle (320)for injecting the output gas into the vacuum chamber, and that the gasinjection system (1000) may further comprise at least one actuator (370)coupled to the nozzle (320) for controlling the location of the nozzle(320) within the vacuum chamber (240). A seal (380) engaging the nozzle(320) at the port (245) of the vacuum chamber (240) is also shownschematically to allow the delivery path (230) to penetrate the wall ofvacuum chamber (240) at the port (245) without leaking air into thevacuum chamber (240). Such a seal (380) may be implemented in one ofseveral ways known to those skilled in the art, including O-rings orbellows, and may be configured to permit the motion of nozzle (320)within vacuum chamber (240). A gas connector (390) enables the removablecartridge (100) to be separated from the delivery path (230) for removaland replacement.

FIG. 12 is a schematic diagram of the components of an exemplaryembodiment of a complete gas injection system (1000) according to thepresent disclosure. The gas injection system (1000) in this embodimentincludes a manifold (250) in the delivery path (230). The manifold (250)is shown here optionally constructed in two pieces including a header.The gas injection system (1000) has at least one precursor valve (330)in the manifold (250) associated with at least one cartridge (100). Inthis embodiment, the precursor valves (330) serve both as outputmetering valves to control the flow of output gas in a continuouslyvariable manner, or, the precursor valves (330) may also be shut offcompletely to function as isolation valves (220), whereby a cartridge(100) may be removed while the vacuum chamber (240) remains under vacuumwhen the associated precursor valve (330) is closed.

FIG. 12 also shows a source of input gas (260) connected through theinput shutoff valve (132) to the reservoir (110) in a cartridge (100).The input passage (140) of a cartridge (100) may be configured eitherwith a direct connection to input shutoff valve (132), or may include anoptional input metering valve (134), whereby the flow of input gas intothe reservoir may be controlled.

FIG. 12 further shows a controller (270) which may comprise aprogrammable computer, further comprising a CPU, memory, program anddata storage, and input/output devices. The controller (270) isoperatively connected to control the input metering valves (134),precursor valves (330), heating elements, and other variable componentsof the gas injection system (1000) in response to instructions, recipes,and/or feedback from sensors. For example, there may be at least onepressure sensor (280) for sensing pressure within the vacuum chamber(240), and a composition sensor (290), such as a residual gas analyzeror optical spectrometer, for sensing the composition of the atmospherewithin the vacuum chamber (240). In general, the output signals from thepressure sensor (280) and the composition sensor (290) are connected tothe controller (270), so that control signals can be computed to controlthe precursor valves (330), operating as output metering valves,according to a predetermined program of operation.

The reader should note that the controller may be any one of aprogrammable computer, an electronic feedback control system (whichmight use analog circuitry), a programmable logic controller (PLC), anembedded microcontroller, or similar devices.

Preferably, an evacuation path (300) that is selectively openablethrough a purge valve (340) is connected to the delivery path (230),where the evacuation path (300) has a conductance higher than theconductance of the delivery path (230), thus allowing the delivery path(230) to be evacuated when desired. The evacuation path may be connectedto the vacuum chamber (240) as shown in FIG. 12, or it may be connectedto a separate vacuum source such as a dedicated vacuum pump. By using ahigher-conductance evacuation path, the delivery path may be evacuatedmore rapidly and thoroughly than by evacuating the delivery path throughthe nozzle (320) into the vacuum chamber (240).

As stated above, each cartridge (100) also has an identification device(200) connectable by wires or wirelessly to a recognition device (210),so that characteristics of a given cartridge (100) may be identified tothe controller (270) as a further input to a program for controlling thegas injection processes. The identification device (200) may be a DIPswitch, or a read-only memory, or a programmable memory, or a wirelesstransponder, preferably holding coded information regarding one or morecharacteristics of the cartridge (100), such as the identification ofthe chemical (180) therein contained. Various other characteristics of acartridge (100) might be usefully identified using identification device(200). The recognition device (210) may be capable of decoding theinformation provided by identification device (200), or it may simply bea disconnectable hardware interface such as a connector plug, connectedto the identification device (200) when the cartridge (100) is mountedin the gas injection system (1000). If the recognition device (210) isnot capable of decoding the coded information itself, then it can conveythe coded information through a communication connection (not shown) toa separate device such as the controller (270) to perform the decodingand interpretation and/or display of the information. The informationregarding characteristics of the cartridge can then be used bycontroller (270) to influence the operation and control of the gasinjection system (1000). For example, recipes stored in the controller(270) might be made available in response to the presence or absence ofcartridges containing certain chemicals. Similarly, safe operation canbe enforced by the controller by using software control of output valvesor precursor valves to prevent the mixing of combinations of outputgases that could react violently or produce dangerous reactionbyproducts.

A recipe stored in the controller (270) can also be designed to bringthe pent-up pressure down to normal levels based upon automaticrecognition of the time since the cartridge (100) was last operated.

In operation, the cartridge (100) is removably connected to the vacuumchamber (240) while keeping the vacuum chamber (240) under vacuum.Through the identification device (200) and the recognition device(210), the characteristics of the cartridge (100) are automaticallyidentified to the programmable computer (270). The pressure sensor (280)and the composition sensor (290) also generate signals communicated tothe programmable computer (270), whereby the gas injection process inthe vacuum chamber (240) may be controlled according to a predeterminedprogram.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementwhich must be included in the claim scope; the scope of patented subjectmatter is defined only by the allowed claims. Moreover, none of theseclaims are intended to invoke paragraph six of 35 U.S.C. Section 112unless the exact words “means for” are used, followed by a gerund. Theclaims as filed are intended to be as comprehensive as possible, and nosubject matter is intentionally relinquished, dedicated, or abandoned.

We claim:
 1. A gas injection system for an energetic-beam instrumenthaving a vacuum chamber, the gas injection system comprising: acartridge capable of containing a chemical serving as a source for anoutput gas to be delivered into the vacuum chamber; a recognition devicefor reading information about the cartridge; and an identificationdevice attached to the cartridge and having coded information regardingone or more characteristics of the cartridge; the identification devicecommunicably connected to the recognition device, such that theidentification device supplies the coded information to the recognitiondevice; and; a controller communicably connected to the recognitiondevice, the controller configured such that it is capable of varying adeposition parameter of the gas injection system, whereby operation ofthe gas injection system may be controlled in response to the codedinformation.
 2. The gas injection system of claim 1, further comprisinga sensor capable of sensing a pressure within the vacuum chambercommunicably connected to the controller, whereby the gas injectionsystem may be controlled in response to the pressure.
 3. The gasinjection system of claim 1, further comprising: a sensor capable ofsensing a composition of an atmosphere within the vacuum chamber; thesensor communicably connected to the controller, whereby the gasinjection system may be controlled in response to the composition. 4.The gas injection system of claim 3, wherein the sensor is a residualgas analyzer.
 5. The gas injection system of claim 3, wherein the sensoris an optical spectrometer.
 6. The gas injection system of claim 1, thecartridge further comprising a reservoir containing the chemical, thechemical rising to a fill line; the fill line having a level defined byan amount of the chemical present in the reservoir at a given time; and,an outlet from the reservoir removably coupled to the delivery path; theoutlet disposed in the reservoir at a level above the level of the fillline and configured so that as the gas injection system is tilted to atilt angle, the outlet remains above the level of the fill line, wherebythe chemical is prevented from entering the vacuum chamber while theoutput gas is being delivered.
 7. A gas injection system for anenergetic-beam instrument having a vacuum chamber, the gas injectionsystem comprising: a chassis mounted to the vacuum chamber; a removablecartridge supported upon the chassis and having an interior and anexterior, and capable of containing a chemical serving as a source foran output gas, the removable cartridge comprising an output passagethrough which the output gas may flow from the interior to the exteriorof the cartridge; a delivery path having a conductance and connectingthe output passage of the removable cartridge to the vacuum chamber,through which the output gas is delivered into the vacuum chamber; andan isolation valve in the delivery path between the cartridge and thevacuum chamber, whereby the cartridge may be removed while the vacuumchamber remains under vacuum when the isolation valve is closed.
 8. Thegas injection system of claim 7, wherein the removable cartridge furthercomprises an output valve.
 9. The gas injection system of claim 8,wherein the output valve further comprises an output metering valve. 10.The gas injection system of claim 7, wherein the delivery path furthercomprises a manifold.
 11. The gas injection system of claim 10, whereinthe isolation valve comprises an isolation valve in the manifoldassociated with the removable cartridge, whereby the cartridge may beremoved while the vacuum chamber remains under vacuum when theassociated isolation valve is closed.
 12. The gas injection system ofclaim 7, wherein the removable cartridge further comprises an inputvalve.
 13. The gas injection system of claim 7, wherein the deliverypath terminates in a nozzle for injecting the output gas into the vacuumchamber; the nozzle having a location in the vacuum chamber.
 14. The gasinjection system of claim 13, further comprising an actuator coupled tothe nozzle for controlling the location of the nozzle within the vacuumchamber.
 15. The gas injection system of claim 7, further comprising: arecognition device for reading information about the removablecartridge; and an identification device attached to the removablecartridge and having coded information regarding one or morecharacteristics of the cartridge, the identification device communicablyconnected to the recognition device, such that the identification devicesupplies the coded information to the recognition device.
 16. The gasinjection system of claim 7, further comprising a controller configuredsuch that it is capable of varying a parameter of the gas injectionsystem, whereby the operation of the gas injection system may becontrolled.
 17. The gas injection system of claim 16, wherein thecontroller further comprises a programmable computer.
 18. The gasinjection system of claim 16, further comprising: a recognition devicefor reading information about the removable cartridge communicablyconnected to the controller; and an identification device attached tothe removable cartridge and having coded information regarding one ormore characteristics of the cartridge, the identification devicecommunicably connected to the recognition device, such that theidentification device supplies the coded information to the recognitiondevice, whereby the gas injection system may be controlled in responseto the coded information.
 19. The gas injection system of claim 16,further comprising a sensor capable of sensing a pressure within thevacuum chamber communicably connected to the controller, whereby the gasinjection system may be controlled in response to the pressure.
 20. Thegas injection system of claim 16, further comprising: a sensor capableof sensing a composition of an atmosphere within the vacuum chamber; thesensor communicably connected to the controller, whereby the gasinjection system may be controlled in response to the composition. 21.The gas injection system of claim 7, the removable cartridge furthercomprising a reservoir containing the chemical, the chemical rising to afill line; the fill line having a level defined by an amount of thechemical present in the reservoir at a given time; and, an outlet fromthe reservoir removably coupled to the delivery path; the outletdisposed in the reservoir at a level above the level of the fill lineand configured so that as the gas injection system is tilted to a tiltangle, the outlet remains above the level of the fill line, whereby thechemical is prevented from entering the vacuum chamber while the outputgas is being delivered.
 22. The gas injection system of claim 21,wherein the removable cartridge further comprises an output valve. 23.The gas injection system of claim 7, further comprising: an evacuationpath having a higher conductance than the delivery path and connectingthe delivery path to a source of vacuum; and a purge valve capable ofopening or closing the evacuation path, whereby the delivery path can beevacuated when the purge valve is opened.
 24. The gas injection systemof claim 23, wherein the source of vacuum is the vacuum chamber of theenergetic beam instrument.
 25. A method of supplying a gas to a vacuumchamber, the method comprising: providing a cartridge enclosing a sourceof a gas, where the cartridge has at least one delivery path having aconductance and selectively openable to the vacuum chamber; removablyconnecting the cartridge to the vacuum chamber while keeping the chamberunder vacuum; identifying one or more characteristics of the cartridgeautomatically; and controlling a flow of the gas from the cartridge intothe vacuum chamber according to the identified characteristics of thecartridge.
 26. The method of claim 25, wherein the step of identifyingfurther comprises transmitting the identified characteristics of thecartridge to a controller.
 27. The method of claim 26, furthercomprising: connecting the controller to a sensor capable of sensing apressure inside the vacuum chamber; and controlling the flow of the gasin response to a signal from the sensor.
 28. The method of claim 25,further comprising a step of evacuating the at least one delivery paththrough an evacuation path having a conductance higher than theconductance of the delivery path.
 29. The method of claim 25, furthercomprising: recognizing the amount of time since the cartridge was lastused; and, controllably releasing the pressure in the cartridge into thevacuum chamber as a function of this time duration.